A name originally applied to nonrigid airships and usually implying small size. Early blimps contained about 100,000 ft³ (2800 m³) and were only a fraction of the size of the rigid airships of that period. The nonrigid pressure-type airship, however, did not stay small; each succeeding model built was substantially larger than its predecessor until ships with volumes of approximately 1,500,000 ft³ (42,000 m³) were operational in the U.S. Navy. With the advent of these larger sizes it appeared that the name blimp would be replaced by the more general term airship. However, the principles of construction of these ships are basically the same regardless of the size.